High-sensitivity Gas Sensor Research Articles

Enhanced adsorption properties of ZnO/GaN heterojunction for CO and H2S under external electric field

The adsorption and electronic properties of CO and H2S adsorbed on ZnO/GaN heterojunction under external electric field (Eext) are investigated by first principle calculations. When the positive Eext is applied, the direction of the built-in electric field and the positive Eext are the same, the adsorption energy (Ead), charge transfer, and bandgap are increased. The positive (negative) breakdown voltages of CO and H2S gases adsorbed on heterojunction are −1.0 V/Å (0.7 V/Å) and −0.7 V/Å (1.2 V/Å), respectively. Interestingly, when a positive and negative Eext is applied, H2S gas is acted as the donor and acceptor, respectively. The ZnO/GaN heterojunction is selective for H2S gas when both CO and H2S are simultaneously adsorbed. When the positions of the gases are exchanged, it is not until the Eext is increased to ±0.2 V/Å that the adsorption process became spontaneous. The larger the Eext is applied, the greater the Ead of gas. It is a more than 150 % and 200 % increase for CO and H2S gases as compared to the absence of Eext. These results reveal that the ZnO/GaN heterojunction can serve as the candidate materials for the high sensitivity gas sensors.

Adsorption of dissolved gas molecules in the transformer oil on silver-modified (002) planes of molybdenum diselenide monolayer: a DFT study

High-sensitivity gas sensor is a crucial online monitoring device to ensure the safe operation of the transformer. In this paper, based on density functional theory, an Ag–MoSe2 monolayer system was established by investigating four different positions of Ag doping to adsorb the dissolved gas (H2, C2H2, CH4, CO and CO2) in transformer oil. The sensing properties of adsorption system for different dissolved gas were studied via the analysis of adsorption energy (E ad), charge transfer, density of state, energy band, lowest unoccupied molecular orbit, highest occupied molecular orbit, and desorption time. Finally, Ag–MoSe2 had good adsorption and desorption properties for CO and CH4 at room temperature, and could be used as a sensor material for the two gases detection. It had strong adsorption and poor desorption performances for C2H2 at room temperature, which could serve as C2H2 scavenger, and simultaneously had good adsorption and desorption performance at a temperature of 358 K, therefore it could be used as a candidate material to detect C2H2 at high temperatures. Ag–MoSe2 had a weak interaction with H2 and CO2, thus was not suitable for detecting the two gases. The results indicated that Ag–MoSe2 had excellent potential in detecting dissolved gases in transformer oil.

High-Sensitive Multi-Gas Detection Based on MDM Waveguide With Symmetric Dual Side-Coupled Ring-Resonators

A high-sensitive multi-parameter gas sensor composed of symmetric dual side-coupled ring resonators in a metallic-dielectric-metallic (MDM) structure is investigated by the finite difference time domain (FDTD) method. The dual side-coupled resonators have lower transmission dip and faster response due to the superposition of the outgoing fields’ amplitude of the symmetric dual resonators, which is very beneficial for detection. Two independently tunable transmission dips are achieved by expanding the ring resonator in ${x}$ -direction, making it possible for dual-parameter sensing. The electric and magnetic distribution characteristics at the two resonant wavelengths are analyzed. Another plasmonic structure expanded along both sides in a central resonator-straight waveguide way is also investigated, and the former structure expanded in ${x}$ -direction works better in detection difficulty and structural utilization. After optimizing the radius and position of ring resonators, the refractive index sensitivities of cavity A and B can reach 2427 nm/RIU and 2431.9 nm/RIU, respectively. The methane and hydrogen sensitivities are −9.213 nm/% and −1.65 nm/% with an extremely high linearity, after coating the methane and hydrogen gas-sensitive film in cavity A and B respectively. This investigation provides an effective way for the design of multi-parameter high-sensitive independently tunable sensors.

Hydrogen bonds-induced room-temperature detection of DMMP based on polypyrrole-reduced graphene oxide hybrids

The development of fast-response, high sensitivity and selectivity gas sensors for monitoring of organophosphorus is essential, where two dimensional graphene-based materials possessing exceptionsal carrier mobility are considered as promising candidates for room-temperature organophosphorus detection. However, it is challenging to fabrication of graphene-based gas sensors for detection of organophosphorus with excellent sensing performances. Herein, we develope a self-redox strategy to synthesize polypyrrole decorated-reduced graphene oxide hybrids (PPy-rGO) by redox reactions between pyrrole and GO during hydrothermal treatment process. This self-redox strategy results in the formation of perfact interfical strucutre between PPy and rGO through the π-π interactions without the impurity from the conventional oxidation/reducing agents. Most importantly, such PPy-rGO hybrids can be used as novel sensing materials for detection of dimethyl methylphosphonate (DMMP) at room temperature. Specially, the response of PPy-rGO-based sensor towards 100 ppm DMMP can reach 12.9 %, which is 3-fold higher than that pristine rGO-based sensor. Meanwhile, PPy-rGO-based sensor exhibits short response time/recovery time (43 s/75 s), low detection limit (5 ppm), excellent repeatability, and high selectivity. By combination of FT-IR and N2 sorption isotherms, the enhanced DMMP sensing performances of PPy-rGO hybrids are concluded as following two aspects. Firstly, the formation of hydrogen bonds between PPy-rGO hybrids and DMMP molecules regulates the adsorption/desorption of DMMP. Secondly, increasing BET surface area by introduction of PPy into rGO matrix is beneficial to DMMP diffusion among the sensing materials. Our work would offer a new strategy for rational development of graphene-based materials for detection of organophosphorus at room temperature.

High-sensitive metal oxide gas sensor for BTEX gases based on ternary composite of Ce x Mn1−x O2/SnO2

A sensitive gas sensor based on a ternary composite of Ce x Mn1−x O2/SnO2 was used for BTEX detection. The ternary Ce x Mn1−x O2/SnO2 was synthesized via hydrothermal and immersion method and characterized by high resolution transmission electron microscopy and x-ray photoelectron spectroscopy. The gas sensor performances were measured on a designed flow-through microsystem consisted of a dynamic multiple gas handling unit, a test gas preheater, an olive-like test chamber and a data analysis apparatus. The developed gas sensor shows a high sensitivity towards BTEX (benzene, toluene, ethylbenzene and xylene) gases with a linear ranging from 100 to 600 ppb at optimal temperature. The sensor exhibited relative selectivity to BTEX gases compared to other VOC components. The sensing mechanism can be concluded as the ‘spillover effects’ of Ce x Mn1−x O2 and heterogeneous effect at the interphase of the Ce x Mn1−x O2–SnO2. The gas sensor developed in this paper provide a possible further application in BTEX gases, especially in ppb-level detection.

Fabrication of room temperature operated ultra high sensitive gas sensor based on mesoporous Ni doped WO3 nanoparticles

Fabrication of room temperature operated ultra high sensitive gas sensor based on mesoporous Ni doped WO3 nanoparticles

Metal-Oxide Based Ammonia Gas Sensors: A Review

This review paper encompasses a study of metal-oxide and their composite based gas sensors used for the detection of ammonia (NH3) gas. Metal-oxide has come into view as an encouraging choice in the gas sensor industry. This review paper focuses on the ammonia sensing principle of the metal oxides. It also includes various approaches adopted for increasing the gas sensitivity of metal-oxide sensors. Increasing the sensitivity of the ammonia gas sensor includes size effects and doping by metal or other metal oxides, which will change the microstructure and morphology of the metal oxides. Different parameters that affect the performances like sensitivity, stability and selectivity of gas sensors are discussed in this paper. Performances of the most operated metal oxides with strengths and limitations in ammonia gas sensing applications are reviewed. The challenges for the development of high sensitive and selective ammonia gas sensors are also discussed.

Performance Investigation of Novel Pt/Pd-SiO2 Junctionless FinFET as a High Sensitive Hydrogen Gas Sensor for Industrial Applications

In this paper, a junctionless (JL) Silicon FinFET (Fin Field effect transistor) has been designed as a hydrogen gas (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) sensor. An analytical model has been developed to analyze the response of junctionless FinFET for detection of hydrogen gas. Palladium is used as a catalytic metal gate. The variation in the gas molecule concentration alters the pressure induced on the catalytic metal gate which changes work function of the metal gate. This variation in metal gate work function is used for detecting the presence of the hydrogen gas. Various electrical parameters for which designed gas sensor is analyzed are- surface potential, threshold voltage, drain current, transconductance, output conductance and charge concentration. The sensitivity analysis in terms of threshold voltage and drain current at different pressures is also carried out. The performance of the sensor with catalytic gate metals-palladium (Pd) and platinum (Pt) is analyzed to find which metal gate gives better response as a hydrogen gas sensor. The JL FinFET is also compared with JL Gate All Around (GAA) transistor for threshold voltage and drain current sensitivity.

High-sensitivity CO electrochemical gas sensor based on a superconductive C-loaded CuO-CeO2 nanocomposite sensing material

The surperconductive C-loaded CuO-CeO2 catalyst was fabricated by a high temperature solid phase reaction. The catalyst was annealed at 500 °C for 4 h then was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM), respectively. The results showed that the as-prepared catalyst was consisted of the particles with the size of 20–50 nm. The gas sensing properties of the superconductive C-loaded CuO-CeO2 to CO were investigated at room temperature. In addition, the as-prepared catalyst exhibited superior activity toward CO. The sensor shows characteristics of a practical-use level: range, 0.1–1000 ppm; sensitivity, 192 mV/ppm; response time, 9 s.

High-sensitive gas-mixture detection based on Mie resonance in slotted MDM metasurface

A high-sensitive gas sensor structure based on Mie resonance in a slotted MDM metasurface is proposed. The sensing performance of slotted and original gold-ring MDM structures is comprehensively compared under the same basic structural parameters. The slotted part can be coated with a gas-sensitive film to construct a new MDM structure in the x-direction, improving the sensitivity effectively with optimized parameters. The detection of mixed gases will not be disturbed. The sensitivity of methane and hydrogen are − 4.516 nm / % and − 1.051 nm / %. The relationship between the polarization angle of the incident light and extinction spectrum is also established to provide feasibility for detecting the polarization angle.

High-sensitivity, fast-response ethanol gas optical sensor based on a dual microfiber coupler structure with the Vernier effect.

A high-sensitivity ethanol gas sensor based on two microfiber couplers and the Vernier effect is examined in this Letter using the unique variation rate conversion point characteristics. The output spectrum of the two couplers connected in parallel are superimposed to form a symmetrical envelope curve, showing high responsivity to variations in the external environment. Ethanol sensitivity was achieved by coating the waist region of the coupler with a mixture of Nile red and polymethyl methacrylate. When the concentration of ethanol gas changes, the envelope spectrum shifts. Experimental results show that a high responsivity of 160 pm/ppm can be obtained by tracing the reference peaks in the envelope curve and that the response and recovery times are on the order of seconds.

High sensitive and selective toxic gas sensor based on monolayer Tetra-MoN2 for sensing NO: A first-principles study

First-principles calculations and non-equilibrium Green’s function calculations have been carried out to investigate the adsorption behaviors of various toxic gas molecules including CO, H2S, NO2, SO2 and NO on the Tetra-MoN2 monolayer in this work. The obtained results manifest that the Tetra-MoN2 monolayer is highly preferable for NO molecules, displaying adequate adsorption energy, distinct charge transfer, which can be attributed to its noticeable atom orbital hybridization. Furthermore, the NO/Tetra-MoN2 system exhibits unique transmission properties and significant work function variation. Such high sensitivity and selectivity of the Tetra-MoN2 monolayer to NO adsorption is conductive to its practical application of gas sensor about NO detection.

Electronic and adsorption properties of the zigzag‐edged triangle graphene nanosheets

AbstractThe electronic and adsorption properties of the zigzag‐edged triangle graphene nanosheets with different size are investigated, including the calculation of the adsorption energy, sensitivity and recovery time after adsorbing CO2, NO2, CH4 and CO. The results show that the quantum size effect is satisfied in the triangle graphene nanosheets, and its conductivity type can be changed from p to n. In addition, the triangle graphene nanosheets with n = 5 has the highest sensitivity to NO2 (374.79%), which is more than 300 times as compared to the lowest one. The recovery time of triangle graphene nanosheets with n = 4 is the shortest, and its sensitivity and recovery time are the best at 144 K. These results reveal that the zigzag‐edged triangular graphene nanosheets can serve as the fundamental structural unit for the design of high sensitivity gas sensors.

Bi-component MOF-derived high-sensitive triethylamine gas sensors based on MoO3/ZnMoO4/CoMoO4 hierarchical structures effectuated by tunable surface/interface transfer behavior

Bi-component MOF-derived high-sensitive triethylamine gas sensors based on MoO3/ZnMoO4/CoMoO4 hierarchical structures effectuated by tunable surface/interface transfer behavior

A high-sensitivity hydrogen gas sensor based on carbon nanotubes fabricated on SiO2 substrate

In this study, an inexpensive simple method for the fabrication of efficient hydrogen (H2) gas sensor based on carbon nanotubes (CNTs) was presented. The CNTs were synthesized using microwave oven and deposited onto SiO2 substrate by a dielectrophoretic method. The as-grown CNTs showed an n-type behavior because CNTs possess the characters of both metallic and semiconductor when placed between the two electrodes, meanwhile, the current was directed mostly by metallic tubes. Upon exposure to H2 gas at room temperature, the CNTs exhibited high sensitivity up to 315% at 140 ppm H2, and relatively good sensitivity of 40% at a very low H2 gas concentration of 20 ppm. To the best of our knowledge, this is the first work involving the fabrication of CNTs for detecting a low H2 gas concentration of 20 ppm at RT with high sensitivity comparing with other previous studies.

Highly Sensitive Gas Sensing Material for Environmentally Toxic Gases Based on Janus NbSeTe Monolayer.

Recently, a new family of the Janus NbSeTe monolayer has exciting development prospects for two-dimensional (2D) asymmetric layered materials that demonstrate outstanding properties for high-performance nanoelectronics and optoelectronics applications. Motivated by the fascinating properties of the Janus monolayer, we have studied the gas sensing properties of the Janus NbSeTe monolayer for CO, CO, NO, NO, HS, and SO gas molecules using first-principles calculations that will have eminent application in the field of personal security, protection of the environment, and various other industries. We have calculated the adsorption energies and sensing height from the Janus NbSeTe monolayer surface to the gas molecules to detect the binding strength for these considered toxic gases. In addition, considerable charge transfer between Janus monolayer and gas molecules were calculated to confirm the detection of toxic gases. Due to the presence of asymmetric structures of the Janus NbSeTe monolayer, the projected density of states, charge transfer, binding strength, and transport properties displayed distinct behavior when these toxic gases absorbed at Se- and Te-sites of the Janus monolayer. Based on the ultra-low recovery time in the order of for NO and NO and for CO, CO, HS, and SO gas molecules in the visible region at room temperature suggest that the Janus monolayer as a better candidate for reusable sensors for gas sensing materials. From the transport properties, it can be observed that there is a significant variation of characteristics and sensitivity of the Janus NbSeTe monolayer before and after adsorbing gas molecules demonstrates the feasibility of NbSeTe material that makes it an ideal material for a high-sensitivity gas sensor.

A high-sensitivity graphene ammonia sensor via aerosol jet printing

High-sensitivity ammonia gas sensors are paramount to many fields in our industries and lives. Due to its complicated fabrication processes, large size and long recovery time of most existing ammonia gas sensors, we present a micron-scale graphene-based ammonia gas sensor using aerosol-jet printing technology. The graphene sensor exhibited high response sensitivity (∼4.64 % for 4.35 ppm NH3 and ∼52.01 % for 97.19 ppm NH3, respectively), short adsorption / desorption time ranging from 50 s to 150 s, good reversibility and repeatability. Further employment of micro-heater close to the sensing line reduced desorption time more than ∼14.3 % when 10 V being applied onto the heater. Such design of the ammonia gas sensor by aerosol-jet printing can give an insight for graphene-based ammonia gas sensors, which may pave a way for the convenient integration with other sensors in portable instruments for coal miners and pathfinders etc.

Sol-Gel 방법으로 제작된 SnO2 seed layer를 적용한 고반응성 ZnO 가스 센서

Sol-Gel 방법으로 제작된 SnO2 seed layer를 적용한 고반응성 ZnO 가스 센서

High Detectivity Ammonia Gas Sensor of Pentacene Based Organic Material with OXIDE MESH

Ammonia gas sensing properties of pentacene based organic gas sensor fabricated by thermal evaporation method on amorphous oxide semiconductor (a-SiInZnO) mesh. The amorphous oxide semiconductor mesh layer was fabricated by RF sputtering and conventional photolithography. Insertion of a dense mesh layer has been found to significantly improve gas sensing properties. In the case of a conventional pentacene thin film, the SEM image analysis resulted in a uniform surface. This means that ammonia gas cannot be adsorbed well on the surface. The insertion of the mesh layer improves the surface volume ratio of the organic thin film and induces more ammonia gas to be adsorbed on the pentacene surface. As a result, it was confirmed that even when the ammonia gas concentration was 5 ppm or less, the detection rate was higher than that of a conventional pentacene thin film. It is expected to be applied to various high-sensitivity organic-based gas sensors.

Multicomponent Sn–Mo–O-containing films formed in anodic alumina matrixes by ionic layer deposition

Multicomponent metal oxide compounds of the composition Sn–Mo–O, Sn–Ni–Mo–O and Sn–Bi–Mo–O were formed by successive ionic layer adsorption and reaction (SILAR) method deposition into anodic alumina matrixes. The growth mechanism of the Sn–Mo–O-containing films in the porous anodic alumina was investigated. It was found that the degree of pore filling, specific thickness and surface morphology of the deposited layer depend not only on the number of cycle’s treatment, but also on the composition of the used solutions. The morphology of Sn–Mo–O and Sn–Ni–Mo–O surfaces had granular structures, while Sn–Bi–Mo–O layer had flake-like structure. The differences in microstructure and deposition of the layers on the surface of the matrixes can be explained by the insufficient activation of anodic alumina pores before deposition. The investigations of the formed layers composition by the electron-probe X-ray spectral microanalysis showed that the ratio of tin to molybdenum in tin-molybdenum containing oxides changes. The Sn/Mo atomic ratio for Sn–Mo–O layer is 1.29/2.72; for Sn–Ni–Mo–O layer is 5.83/4.85; for Sn–Bi–Mo–O layer is 0.60/0.87. The using of SILAR method allows forming multicomponent films in the anodic alumina matrixes, which have great potential to applicate in high-sensitivity gas sensors.